PIMPL Node + remove all Natron:: from Node.cpp
avoid all the #ifdef NATRON_LOG by using a no-op class, and add the function Log::enabled() (to be used if one wants to avoid useless log-dedicated computation)
Merge branch 'workshop' of https://github.com/MrKepzie/Natron into workshop

Conflicts:
	Engine/Node.cpp
Fixed exr writer to render any image size
Lut.cpp algorithms now render with (0,0) at bottom left instead of top left
Cleaned-up ViewerGL constructor. Also added files for the upcoming Curve editor
Any TabWidget can now be full screen
Nodegraph is the active widget in the workshop pane by default
Added RectD class
Temp algorithm for scale display of the curve editor
Added missing includes
Added implementation of algorithms Scale1 scale2 and Scale3 of ACM
Fixed conflicts
Switched from Scale1 to Scale2 for test.
Viewer and Curve Editor now takes into account properly the pixel aspect ratio.
bug fix: alpha is not in 0..1 but in 0..255, and is integer!
use standard includes
Lut: separate premult functions
ScaleSlider is now inheriting QGLWidget
Merge branch 'workshop' of github.com:MrKepzie/Natron into workshop